Effect of 8-oxoguanine glycosylase deficiency on aflatoxin B1 tumourigenicity in mice

The mycotoxin aflatoxin B-1 (AFB(1)) may initiate cancer by causing oxidatively damaged DNA, specifically by causing 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) lesions. Base excision repair removes these lesions, with 8-oxoguanine glycosylase (OGG1) being the rate-limiting enzyme. The aim of this study was to determine the effect of ogg1 deficiency on AFB(1)-induced oxidatively damaged DNA and tumourigenesis. Female wild-type, heterozygous and homozygous ogg1 null mice were given a single dose of 50mg/kg AFB(1) or 40 A mu l dimethyl sulfoxide (DMSO) ip. Neither ogg1 genotype nor AFB(1) treatment affected levels of oxidised guanine in lung or liver 2h post-treatment. AFB(1)-treated ogg1 null mice showed exacerbated weight loss and mortality relative to DMSO-treated ogg1 null mice, but AFB(1) treatment did not significantly increase lung or liver tumour incidence compared with controls, regardless of ogg1 genotype. Suspect lung masses from three of the AFB(1)-treated mice were adenomas, and masses from two of the mice were osteosarcomas. No osteosarcomas were observed in DMSO-treated mice. All liver masses from AFB(1)-treated mice were adenomas, and one also contained a hepatocellular carcinoma. In DNA from the lung tumours, the K-ras mutation pattern was inconsistent with initiation by AFB(1). In conclusion, ogg1 status did not have a significant effect on AFB(1)-induced oxidatively damaged DNA or tumourigenesis, but deletion of one or both alleles of ogg1 did increase susceptibility to other aspects of AFB(1) toxicity.